Java 正则表达式从 URL 中提取主机名和域名

Question

I have already viewed and tried multiple other threads and doesn't work for me. I need the regex solution for it to work and no java code that does it without regex.

Some of the threads which I have already checked: Get domain name from given url , Extract host name/domain name from URL string , and Java regex to extract domain name? None work for me, either the regex doesn't work or the solution is a java code without regex.

What I am trying to do?

Case 1:
Input: https://api.twitter.com/blog/category/2?user=42&status=enabled
Output: api.twitter.com

Input: abc.xyz.com/blog/category/2?user=42&status=enabled
Output: abc.xyz.com

Case 2:
Input: https://abc.xyz.com/blog/category/2?user=42&status=enabled
Output: xyz.com

Input: abc.xyz.com/blog/category/2?user=42&status=enabled
Output: xyz.com

I need 2 regexes to solve each case mentioned above. If it can be done in one, even that works.

I tried the below regex from the first post:

^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?

This one works when there is https:// or any scheme but fails when there is no scheme in the URL.

So far I am solving the first case using a 2 step solution.

Step 1: Replace scheme
(.*://)(.*) -> $2
remove anything before and including string "://"

Step 2: Extract host name
([^/]*)(.*) -> $1
The first group extracts everything that is before the first "/". Basically extracting everything that isn't slash till I see the first one. 

Answer 1

You may use this regex with optional matches and capture groups:

^(?:\w+://)?((?:[^./?#]+\.)?([^/?#]+))

RegEx Demo

RegEx Details:

• ^ : Start
• (?:\w+://)? : Optionally match scheme names followed by ://
• ( : Start capture group #1
  • (?:[^./?#]+\.)? : Optionally match first part of domain name using a non-capture group
  • ([^/?#]+) : Match 1+ of any character that is not / , ? , # in capture group #2
• ) : End capture group #1